In many printing systems, it is common practice to develop a hardcopy of an image by using a photoconductive surface. The photoconductive surface is selectively charged with a latent electrostatic image having image and background areas. A liquid developer comprising charged toner particles in a carrier liquid is brought into contact with the selectively charged photoconductive surface. The charged toner particles adhere to the image areas of the latent image while the background areas remain clean. A hardcopy material (e.g. paper) is brought directly or indirectly into contact with the photo-conductive surface in order to transfer the latent image. Variations of this method utilize different ways for forming the electrostatic latent image on a photoreceptor or on a dielectric material.
Typically the liquid developer (also referred to herein as ink or toner) comprises a thermoplastic resin (polymer) as the basis for the toner particles (also referred to herein as ink particles), and a non-polar liquid as a carrier liquid in which the toner particles are dispersed. Generally, the toner particles contain a colorant such as a pigment.
A charge director, also called charge control agent or imaging agent, is also added to the dispersion to induce charge on the particles. As known in the art, a charge adjuvant may be added to increase the charging effect of the charge director.
US 2004/0241567, the disclosure of which is incorporated herein by reference, describes a liquid developer for image forming apparatus, and mentions that “[o]ther charge control agents to be used include: metal salts of dialkyl sulfosuccinate . . . ”.
U.S. Pat. No. 4,585,535, and its divisional, U.S. Pat. No. 4,719,026 the disclosures of both are incorporated herein by reference, relate to a method of electrophoretically depositing a ferromagnetic material on a tape to produce high density recording media, and explains that “[t]here are two apparently different kinds of charge directors. In the first, the charge director in ISOPAR has a conductivity measured at 1 kHz that is larger than the conductivity obtained when it is mixed with toner particles. Lecithin and barium petronate are examples. In second case, the charge director in ISOPAR has almost no conductivity . . . . Barium sulfocuccinate (BaOT) and salts of bistridecyl sulfosuccinate are examples of this case.”
Synthesis of various metal salts of di-2-ethyl-hexyl-sulfosuccinate salts from sodium salts of same anion is described in Bull. Soc. Chim. Belg. 1979, 88(1-2), 31-36 the disclosure of which is incorporated herein by reference.
Other documents that relate to salts of bistridecyl sulfosuccinate are: U.S. Pat. No. 6,669,984, U.S. Pat. No. 6,270,884, U.S. Pat. No. 5,246,916, U.S. Pat. No. 4,990,416; U.S. Pat. No. 6,958,091, U.S. Pat. No. 6,946,028; U.S. Pat. No. 6,899,757, U.S. Pat. No. 6,897,251, U.S. Pat. No. 6,235,100, U.S. Pat. No. 5,889,162, U.S. Pat. No. 5,679,724, U.S. Pat. No. 5,595,723, U.S. Pat. No. 5,558,855, and U.S. Pat. No. 4,766,061, the disclosures of all of which are incorporated herein by reference.